Biometric authentication is a technique to perform identity verification using features (hereinafter also referred to as “biometric features”) of biometric information, such as fingerprint, face, vein, or the like. The biometric authentication matches biometric features (hereinafter also referred to as “registered biometric features”) that are registered in advance to biometric features that are acquired when confirmation is required, in order to perform the identity verification based on whether the acquired biometric features match the registered biometric features.
Terminal apparatuses, such as a tablet terminal or the like, provided with a biometric authentication function, include a terminal apparatus that performs a palm vein authentication. When acquiring vein information for the palm vein authentication, it is desirable to capture the palm from a position slightly separated from the terminal apparatus, so that the entire palm can be captured. However, when the terminal apparatus is held by one hand to capture the palm of the other hand, a position of a region of the palm that is captured becomes unstable, and the authentication failing rate increases even though the identity verification is performed on the person himself (that is, FRR (False Rejection Rate) increases).
When the hand holding the terminal apparatus is captured in a state in which the terminal apparatus is held by the hand, the position of the region of the palm that is captured stabilizes. However, in this case, a distance between the palm and the terminal apparatus becomes short. For this reason, only a portion of the palm can be captured, and it is difficult to capture the entire palm. In addition, the position where the terminal apparatus is held by the hand is not necessarily always constant. Accordingly, a so-called partial authentication may be performed by registering the features of the vein information (hereinafter also referred to as “vein pattern”) of the entire palm, capturing only a portion of the vein pattern at a time of matching, and partially matching the features of the captured vein pattern to the registered features of the corresponding portion of the vein pattern of the entire palm.
The partial authentication is a technique used in fingerprint authentication, for example. For example, Japanese Laid-Open Patent Publication No. 2002-024831 proposes the partial authentication used in the fingerprint authentication. The partial authentication used in the fingerprint authentication determines the position of a fingerprint portion captured using a center of a whorl of the fingerprint as a reference with respect to the entire fingerprint, and performs the partial matching to the corresponding fingerprint portion of the registered fingerprint. Hence, the position of the captured fingerprint portion can be determined with ease, and the partial matching of the fingerprint can be performed at a high speed with a high accuracy.
On the other hand, in the case of the vein authentication, the vein pattern of a portion of the captured palm does not include information, such as the whorl of the fingerprint, that may be used as a reference for the position with respect to the entire palm. For this reason, in a case in which the partial authentication is applied to the vein authentication, it is conceivable to determine the position of the vein pattern of the portion of the captured palm with respect to the entire palm, and perform the partial matching of the features to a corresponding portion of the registered vein pattern. However, in the partial authentication using the vein pattern of the portion of the captured palm, there are cases in which position information, such as contours of fingers and palm, is not included in the captured information. In such cases, it is difficult to determine the position of the vein pattern of the portion of the captured palm with respect to the entire palm. Consequently, the vein pattern of the entire palm must be scanned by the vein pattern of the portion of the captured palm, to find a matching position and perform the partial matching to the features of the corresponding portion of the registered vein pattern. As a result, it takes time to scan the vein pattern of the entire palm, and a time required to perform the matching process increases. In addition, there is a possibility that the features of the vein pattern of one portion of the captured palm of a user match by chance to features of one portion of a vein pattern of the entire palm of a different user.
Accordingly, it is conventionally difficult to perform a vein authentication at a high speed in a case in which the partial authentication is applied to the vein authentication.
Other related art includes Japanese Laid-Open Patent Publications No. 2010-202029 and No. 2013-200673, for example.